The present invention is directed to an anchor lock fastening assembly (ALFA) which provides the function of holding the rail to the railroad tie while at the same time preventing longitudinal displacement of the rail. More particularly, the present invention is directed to a floating rail fastening assembly wherein limited vertical movement between the floating rail and the railroad cross tie is provided by an anchoring system which avoids the use of compressive forces (toe loads) for anchoring the rail as utilized by the prior art.
Most of the rail fastening devices of the prior art fall into one of the following categories. A first category is a positive fastening-type device which exerts a toe load of approximately 4,000 to 6,000 pounds on the base of the rail by means of a set of spring clips or spring loaded caps anchored by means of inserts or shoulders cast into the concrete tie. Exemplary of this type of device is shown in the PORTEC advertisement entitled Sidewinder (the system). Other similar types of devices are shown in the UNIT-D.E. SPRING CLIP advertisement by UNIT-D.E. INC. In all such devices, because of the toe load fastening, the ties tend to follow the vertical movements of the rail under the pulsating loads of passing trains which, particularly under wet environmental conditions, produces a a suction effect which causes subgrade material to migrate into the ballast, thereby adversely affecting drainage roadbed stability and the structural integrity of the ties. In addition, the high toe loads required by the positive fastening device substantially compresses the cushioning pads used in conjunction with the tie, thereby unloading the clips and causing rail slippage. If damaged, the clip retaining inserts or shoulders often necessitate the replacement of the entire cross tie.
The second type of rail fastening device known in the prior art is a rail free or floating fastening which does not provide a toe loading function as described hereinabove but rather utilizes a combination of cut spike and anchor wherein the spike is driven into the tie in such a manner as to permit limited vertical movement between the tie plate and the base of the rail. The anchor prevents the rail from creeping or slipping, that is, moving longitudinally under the effect of forces caused by temperature changes in the rail or by accelerating or decelerating trains. With few exceptions, the positive fastening device is a typical European design for both wood and concrete tie whereas the rail free cut spike and anchor fastening device is commonly utilized in the United States. It should be noted however that the concrete tie together with positive fastenings is being tested on numerous test sites in the United States where fastening performance is a matter of growing concern.
Although the rail free or floating fastening device of the prior art which is utilized on wooden ties, provides an economical method of fastening the rails to the ties, the increased loads produced on the rail by modern, heavy freight trains tend to cause rail roll-over and gage widening. As a result the spikes become loose, necessitating frequent repair of the ties and regaging of the rails which substantially reduces the life of the railroad tie. In addition, varying installation conditions adversely affect the fastening effect or holding power of the cut spikes which act like splitting wedges in the railroad ties. This type of fastening cannot be used on concrete ties although anchors are sometimes used to prevent rail movements occurring with clip type fastenings.
Accordingly, an object of the present invention is to provide an anchor lock rail fastening assembly which substantially eliminates the problems encountered in the prior art devices, such as is exemplified by the positive fastening devices and the conventional rail free or floating fastening device.
Another object of the present invention is to provide a floating rail fastening assembly wherein limited vertical movement between the floating rail and the railroad cross tie is achieved by an anchoring system which avoids the use of compressive forces (toe loads) for anchoring the rail to the tie.
A further object of the present invention is to provide an anchor lock rail fastening assembly which consists of a minimum number of components, allows for mechanized assembly, and is substantially maintenance free.
Still another object of the present invention is to provide a floating rail fastening assembly which provides substantially improved rail-wheel contact for high speed operation.
Yet another object of the present invention is to provide a fail-safe electrical insulating device.
A still further object of the present invention is to provide a fastening device that can be used both on wood and concrete ties.
Yet a further object of the present invention is to provide a fastening device that makes possible the choice of a rail cushioning pad, the resilience of which is a function of the load to be cushioned rather than to suit the spring rate of a particular clip design.
Still another object of the present invention is to provide a fastening device that provides permanent longitudinal and lateral restraint of the rail.
Yet another object of the present invention is to provide a fastening device, which if damaged, does not in turn cause damage or loss of the concrete tie.
Another object of the present invention is to provide a fastening device that resists both corrosion and abrasion.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Pursuant to the present invention, the prior art disadvantages have been eliminated and the objects of the present invention have been achieved by providing an anchor lock rail fastening assembly. According to the present invention, the proposed anchor lock rail fastening assembly incorporates a novel anchor lock which by passively restricting the vertical movement of a known spring type anchor, is effective in dispensing with toe loading of rails on concrete ties and the use of rail spikes on wood ties.